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Compressible nozzle flow  no problem for fluent but impossible with openFOAM? 

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November 23, 2021, 10:45 
Compressible nozzle flow  no problem for fluent but impossible with openFOAM?

#1 
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Hello everybody,
after struggling with that case for a long while now, I need some help with openFOAM. Perhaps there is someone out there who could give me some guidance. I'm working on a 2D axisymmetric model of the compressible flow through a convergingdiverging nozzle. After the flow leaves the nozzle it passes a backwards facing step: Bild1.png Solving for the same geometry and mesh fluent converges smoothly within a few thousand iterations. This holds for the realizable kepsilon (nonequilibrium wall function) and the komega turbulence model both with viscous heating enabled. The solver configuration is as follows:
Boundary conditions are:
However, when I tried to rebuild the case with openFOAM I'm unable to get a converged solution. With the realizable kepsilon model the solver at least doesn't crash but with the komega it will blow up within a couple of iterations. In both cases the time step continuity errors are huge while the linear solvers for the different fields show small residuals. What I did so far:
Code:
// * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // Create time Create mesh for time = 0 Time = 0 Mesh stats points: 432246 internal points: 0 faces: 861240 internal faces: 428995 cells: 215250 faces per cell: 5.99412311266 boundary patches: 7 point zones: 0 face zones: 0 cell zones: 0 Overall number of cells of each type: hexahedra: 213985 prisms: 1265 wedges: 0 pyramids: 0 tet wedges: 0 tetrahedra: 0 polyhedra: 0 Checking topology... Boundary definition OK. Cell to face addressing OK. Point usage OK. Upper triangular ordering OK. Face vertices OK. Number of regions: 1 (OK). Checking patch topology for multiply connected surfaces... Patch Faces Points Surface topology inlet 50 101 ok (nonclosed singly connected) outlet 240 481 ok (nonclosed singly connected) upperWall 1455 2912 ok (nonclosed singly connected) lowerWall 0 0 ok (empty) frontAndBack 0 0 ok (empty) frontAndBack_pos 215250 216756 ok (nonclosed singly connected) frontAndBack_neg 215250 216756 ok (nonclosed singly connected) Checking faceZone topology for multiply connected surfaces... No faceZones found. Checking basic cellZone addressing... No cellZones found. Checking geometry... Overall domain bounding box (0 0 0.000436193873653) (0.08 0.01 0.000436193873653) Mesh has 2 geometric (nonempty/wedge) directions (1 1 0) Mesh has 3 solution (nonempty) directions (1 1 1) Wedge frontAndBack_pos with angle 2.49762357054 degrees Wedge frontAndBack_neg with angle 2.49762357054 degrees All edges aligned with or perpendicular to nonempty directions. Boundary openness (4.32643646952e18 2.00893658027e17 8.27156673543e16) OK. Max cell openness = 3.03021770314e16 OK. Max aspect ratio = 10.4202379507 OK. Minimum face area = 3.28108080426e11. Maximum face area = 1.34703394904e07. Face area magnitudes OK. Min volume = 1.00959120606e15. Max volume = 1.27411305502e11. Total volume = 2.53751454593e07. Cell volumes OK. Mesh nonorthogonality Max: 23.0894947956 average: 3.34709052281 Nonorthogonality check OK. Face pyramids OK. Max skewness = 0.568549620689 OK. Coupled point location match (average 0) OK. Mesh OK.
There are many similar questions in this forum, e.g.: But most of the suggested solutions concern the above already mentioned modifications: bounded schemes vs. unbounded, small under relaxation factors or no relaxation at all, problems with the mesh, or problems with the boundary conditions. Using the bounded schemes stops the negative values for the turbulence variables. But I did not get rid of the high time step continuity errors. Perhaps my boundray conditions are wrong because the incompressible case did not converge, too. I would really appreciate any help in solving this problem. Best regards, Ralf These are my case files: 0/alphat: Code:
dimensions [1 1 1 0 0 0 0]; internalField uniform 1e3; boundaryField { inlet { type calculated; value $internalField; } outlet { type calculated; value $internalField; } upperWall { type compressible::alphatWallFunction; value $internalField; } lowerWall { type symmetryPlane; } frontAndBack { type empty; } frontAndBack_pos { type wedge; } frontAndBack_neg { type wedge; } } Code:
dimensions [0 2 3 0 0 0 0]; internalField uniform 200; boundaryField { inlet { type turbulentMixingLengthDissipationRateInlet; mixingLength 5.96e3; value uniform 200; } outlet { type zeroGradient; value uniform 200; } upperWall { type epsilonWallFunction; value uniform 200; } lowerWall { type symmetryPlane; } frontAndBack { type empty; } frontAndBack_pos { type wedge; } frontAndBack_neg { type wedge; } } Code:
dimensions [0 2 2 0 0 0 0]; internalField uniform 1; boundaryField { inlet { type turbulentIntensityKineticEnergyInlet; intensity 0.05; value uniform 1; } outlet { type zeroGradient; value uniform 1; } upperWall { type kqRWallFunction; value uniform 1; } lowerWall { type symmetryPlane; } frontAndBack { type empty; } frontAndBack_pos { type wedge; } frontAndBack_neg { type wedge; } } Code:
dimensions [0 2 1 0 0 0 0]; internalField uniform 0; boundaryField { inlet { type calculated; value $internalField; } outlet { type calculated; value $internalField; } upperWall { type nutkWallFunction; value $internalField; } lowerWall { type symmetryPlane; } frontAndBack { type empty; } frontAndBack_pos { type wedge; } frontAndBack_neg { type wedge; } } Code:
dimensions [1 1 2 0 0 0 0]; internalField uniform 101325; boundaryField { inlet { type zeroGradient; } outlet { type fixedValue; value uniform 101325; } upperWall { type zeroGradient; } lowerWall { type symmetryPlane; } frontAndBack { type empty; } frontAndBack_pos { type wedge; } frontAndBack_neg { type wedge; } } Code:
dimensions [0 0 0 1 0 0 0]; internalField uniform 298; boundaryField { inlet { type fixedValue; value $internalField; } outlet { type inletOutlet; inletValue $internalField; value $internalField; } upperWall { type zeroGradient; } lowerWall { type symmetryPlane; } frontAndBack { type empty; } frontAndBack_pos { type wedge; } frontAndBack_neg { type wedge; } } Code:
dimensions [0 1 1 0 0 0 0]; internalField uniform (0 0 0); boundaryField { inlet { type flowRateInletVelocity; massFlowRate constant 4e5; //massFlowRate tableFile; //file "system/mdottable"; //outOfBounds clamp; rhoInlet 1; } outlet { type inletOutlet; inletValue uniform (0 0 0); value uniform (0 0 0); } upperWall { type noSlip; } lowerWall { type symmetryPlane; } frontAndBack { type empty; } frontAndBack_pos { type wedge; } frontAndBack_neg { type wedge; } } Code:
thermoType { type hePsiThermo; mixture pureMixture; transport const; thermo hConst; equationOfState perfectGas; specie specie; energy sensibleInternalEnergy; } mixture { specie { nMoles 1; molWeight 28.966; } thermodynamics { Cp 1006.43; Hf 2.544e+6; } transport { mu 1.7894e05; Pr 0.737; } } Code:
simulationType RAS; RAS { RASModel realizableKE; turbulence on; printCoeffs on; } Code:
application rhoSimpleFoam; startFrom latestTime; startTime 0; stopAt endTime; endTime 25000; deltaT 1; writeControl timeStep; writeInterval 500; purgeWrite 0; writeFormat ascii; writePrecision 12; writeCompression off; timeFormat general; timePrecision 12; runTimeModifiable true; functions { #includeFunc mag(U) #includeFunc flowRatePatch(name=inlet) #includeFunc flowRatePatch(name=outlet) #includeFunc patchAverage(name=inlet,p) minmaxdomain { type fieldMinMax; libs (fieldFunctionObjects); enabled true; //true or false mode component; writeControl outputTime; log true; fields (p U ); //k epsilon omega nut); } yplus { type yPlus; libs (fieldFunctionObjects); enabled true; writeControl outputTime; } writecellvol { type writeCellVolumes; libs (fieldFunctionObjects); enabled true; writeControl outputTime; } integralLenghtScale { // Mandatory entries (unmodifiable) type turbulenceFields; libs (fieldFunctionObjects); // Mandatory entries (runtime modifiable) // Either field or fields entries field L; enabled true; writeControl outputTime; } } Code:
temperature_constraints { type limitTemperature; selectionMode all; active true; limitTemperatureCoeffs { selectionMode all; min 1; max 5000; } } Code:
ddtSchemes { default steadyState; } gradSchemes { default cellLimited Gauss linear 1; //faceLimited leastSquares 1.0; } divSchemes { default none; div(phi,U) bounded Gauss linearUpwind default; //Gauss limitedLinearV 1.0; div(phi,k) bounded Gauss linearUpwind default; //Gauss limitedLimitedLinear 1.0 1e8 1e10; div(phi,epsilon) bounded Gauss linearUpwind default; //Gauss limitedLimitedLinear 1.0 1e8 1e10; div(((rho*nuEff)*dev2(T(grad(U))))) Gauss linear; div(phi,e) bounded Gauss linearUpwind default; //bounded Gauss upwind; div(phi,Ekp) bounded Gauss linearUpwind default; //bounded Gauss upwind; div(phid,p) Gauss limitedLinear 1.0; div((phiinterpolate(rho)),p) Gauss limitedLinear 1.0; } laplacianSchemes { default Gauss linear limited 1; } interpolationSchemes { default linear; } snGradSchemes { default limited 1; } Code:
solvers { p { solver GAMG; tolerance 1e07; relTol 0; smoother GaussSeidel; nCellsInCoarsestLevel 400; } "(UekepsilonnuTilda)" { solver GAMG; tolerance 1e07; relTol 0; smoother GaussSeidel; nCellsInCoarsestLevel 400; } } SIMPLE { nNonOrthogonalCorrectors 0; transonic yes; consistent no; residualControl { p 1e5; U 1e6; e 1e5; "(kepsilonnuTilda)" 1e5; } } relaxationFactors { fields { p 0.3; } equations { U 0.9; e 0.8; k 0.9; epsilon 0.9; nuTilda 0.8; } } 

November 24, 2021, 08:38 

#2 
Senior Member

Greetings,
rhoSimpleFoam solves conservation of mass, momentum and energy. The boundary conditions (inlet especially) should be compatible with the coupling of pressure, velocity and temperature. This makes a compressible rhoSimpleFoam case harder to set up than an incompressible simpleFoam case. The ideal gas law defines a relation between temperate, pressure and density (and thus velocity through mass flow rate). Fixing two quantities, the third one can be determined. This means that temperature, pressure and density can *not* be set (or user defined) independently from each other. In my case, e.g., it proved to be valuable to fix inlet pressure (e.g p = 101325 Pascal) and inlet temperature (e.g. T = 773.15 K) to arrive at density rho = p / (R_{specific} * T) = 101325 / (287.058 * 773.15) = 0.45654 kg/m^3 . Given density and area of the inlet, the inlet velocity can be determined. In your case setup, I fail to understand the inlet Gauge pressure set to 0. My understanding is that you are very close to a working solution. Good luck. 

November 24, 2021, 11:19 

#3 
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Thank you very much for your reply.
The "Initial Gauge Pressure" is only specified in the fluent case. As far as I understand it is used only for initialization. The openFOAM case uses a zeroGradient boundary condition at the inlet. I thought with that BC the pressure itself is not specified and the ideal gas law is used as you described to calculate it from the fixed velocity and temperature. In the meanwhile I rebuilt an incompressible case from scratch and the simpleFoam solver converges really smoothly within 2000 iterations for the same BCs on pressure, velocity and turbulence as mentioned above. The moment I change from incompressible to compressible(*) the solver crashes. (*) by  adding thermophysicalProperties,  changing pressure from m^2/s^2 to kg/(m*s^2) in 0/p,  adding rho to massFlowRate in 0/U,  adding 0/T and 0/alphat,  modifying divScheme for the shearrate tensor (rho*...),  adding the schemes and solver for the energy eq. I noticed that the convergence strongly depends on the gradient schemes for the incompressible case. While kEpsilon is fine with "Gauss linear" the kOmega works only when gradSchemes is set to "cellLimited leastSquares 1". Perhaps the crashes result from the wrong schemes or solver settings.. Are there any recommendations for compressible internal flows? 

November 24, 2021, 11:50 

#4 
Senior Member

My bad: pressure indeed has zeroGradient on the inlet patch as you suggest.
What do you mean by "solver crashing"? What happens exactly? Can you share solver log file? What happens is case that rho on inlet is increased from 1 to 100, say (increasing density should decrease velocity at same mass flow rate)? Does this lowering of the inlet velocity make the case easier to converge? 

November 24, 2021, 16:06 

#5 
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By crashing I mean the solver stops more or less rapidly.
I think these are floating point exceptions visible in this example but I have no idea where they come from. Code:
/**\  =========    \\ / F ield  OpenFOAM: The Open Source CFD Toolbox   \\ / O peration  Version: v2012   \\ / A nd  Website: www.openfoam.com   \\/ M anipulation   \**/ Build : _7bdb50949420201222 OPENFOAM=2012 Arch : "LSB;label=32;scalar=64" Exec : rhoSimpleFoam Date : Nov 24 2021 Time : 21:40:22 Host : xxxx PID : 6509 I/O : uncollated Case : run/darm22_RhoSimpleFoam_mdot_kOmegaSST3 nProcs : 1 trapFpe: Floating point exception trapping enabled (FOAM_SIGFPE). fileModificationChecking : Monitoring runtime modified files using timeStampMaster (fileModificationSkew 5, maxFileModificationPolls 20) allowSystemOperations : Allowing usersupplied system call operations // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // Create time Create mesh for time = 0 SIMPLE: convergence criteria field p tolerance 0.01 field U tolerance 0.001 field "(keepsilonomegafv2)" tolerance 0.001 Reading thermophysical properties Selecting thermodynamics package { type hePsiThermo; mixture pureMixture; transport const; thermo hConst; equationOfState perfectGas; specie specie; energy sensibleInternalEnergy; } Reading field U Reading/calculating face flux field phi Creating turbulence model Selecting turbulence model type RAS Selecting RAS turbulence model kOmegaSST Selecting patchDistMethod meshWave RAS { RASModel kOmegaSST; turbulence on; printCoeffs on; alphaK1 0.85; alphaK2 1; alphaOmega1 0.5; alphaOmega2 0.856; gamma1 0.555555555556; gamma2 0.44; beta1 0.075; beta2 0.0828; betaStar 0.09; a1 0.31; b1 1; c1 10; F3 false; decayControl false; kInf 0; omegaInf 0; } No MRF models present Creating finite volume options from "system/fvOptions" Selecting finite volume options type limitTemperature Source: temperature_constraints  selecting all cells  selected 215250 cell(s) with volume 2.53751454593e07 Starting time loop surfaceFieldValue flowRatePatch(name=inlet): operation = sum surfaceFieldValue flowRatePatch(name=outlet): operation = sum surfaceFieldValue patchAverage(name=inlet,p): operation = areaAverage turbulenceFields integralLenghtScale: storing fields: turbulenceProperties:L Time = 1 smoothSolver: Solving for Ux, Initial residual = 1, Final residual = 0.0728821995915, No Iterations 3 smoothSolver: Solving for Uy, Initial residual = 0, Final residual = 0, No Iterations 0 smoothSolver: Solving for Uz, Initial residual = 0, Final residual = 0, No Iterations 0 smoothSolver: Solving for e, Initial residual = 0.999955154113, Final residual = 0.0982901196004, No Iterations 3 limitTemperature temperature_constraints Lower limited 0 (0%) of cells limitTemperature temperature_constraints Upper limited 0 (0%) of cells limitTemperature temperature_constraints Unlimited Tmax 298 Unlimited Tmin 298 GAMG: Solving for p, Initial residual = 0.999999999373, Final residual = 0.0610521226431, No Iterations 21 time step continuity errors : sum local = 5.14879974762, global = 0.0250572123018, cumulative = 0.0250572123018 smoothSolver: Solving for omega, Initial residual = 0.163249893053, Final residual = 0.0138597003377, No Iterations 3 bounding omega, min: 31743.4509378 max: 10700467.3544 average: 79932.7997844 smoothSolver: Solving for k, Initial residual = 1, Final residual = 0.0721647330784, No Iterations 5 ExecutionTime = 4.68 s ClockTime = 5 s Time = 2 smoothSolver: Solving for Ux, Initial residual = 0.307889634693, Final residual = 0.0206100973894, No Iterations 4 smoothSolver: Solving for Uy, Initial residual = 0.429556159428, Final residual = 0.0429469947432, No Iterations 3 smoothSolver: Solving for Uz, Initial residual = 0.502502639153, Final residual = 0.0112927535803, No Iterations 1 smoothSolver: Solving for e, Initial residual = 0.999956608923, Final residual = 0.0255575610827, No Iterations 2 limitTemperature temperature_constraints Lower limited 0 (0%) of cells limitTemperature temperature_constraints Upper limited 0 (0%) of cells limitTemperature temperature_constraints Unlimited Tmax 298.02092684 Unlimited Tmin 298 GAMG: Solving for p, Initial residual = 0.00282266766787, Final residual = 0.000277825629673, No Iterations 12 time step continuity errors : sum local = 3102.24138499, global = 1592.12762623, cumulative = 1592.15268344 smoothSolver: Solving for omega, Initial residual = 0.051531840972, Final residual = 0.00407122098254, No Iterations 1 bounding omega, min: 1743823.00544 max: 4006080691.61 average: 89426.2874374 smoothSolver: Solving for k, Initial residual = 0.327474312565, Final residual = 0.0122084139505, No Iterations 2 bounding k, min: 1.09712825705 max: 14.4920020548 average: 0.389117493712 ExecutionTime = 7.67 s ClockTime = 8 s Time = 3 smoothSolver: Solving for Ux, Initial residual = 0.117821454106, Final residual = 0.00901320173028, No Iterations 2 smoothSolver: Solving for Uy, Initial residual = 0.0927055396049, Final residual = 0.0089339016751, No Iterations 2 smoothSolver: Solving for Uz, Initial residual = 0.375478299784, Final residual = 0.0141813272293, No Iterations 1 smoothSolver: Solving for e, Initial residual = 0.279167325572, Final residual = 0.0118560063607, No Iterations 2 limitTemperature temperature_constraints Lower limited 8 (0.00371660859466%) of cells limitTemperature temperature_constraints Upper limited 0 (0%) of cells limitTemperature temperature_constraints Unlimited Tmax 415.915872131 Unlimited Tmin 176.302097449 #0 Foam::error::printStack(Foam::Ostream&) at ??:? #1 Foam::sigFpe::sigHandler(int) at ??:? #2 ? in /lib64/libpthread.so.0 #3 Foam::GAMGSolver::scale(Foam::Field<double>&, Foam::Field<double>&, Foam::lduMatrix const&, Foam::FieldField<Foam::Field, double> const&, Foam::UPtrList<Foam::lduInterfaceField const> const&, Foam::Field<double> const&, unsigned char) const at ??:? #4 Foam::GAMGSolver::Vcycle(Foam::PtrList<Foam::lduMatrix::smoother> const&, Foam::Field<double>&, Foam::Field<double> const&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::Field<double>&, Foam::PtrList<Foam::Field<double> >&, Foam::PtrList<Foam::Field<double> >&, unsigned char) const at ??:? #5 Foam::GAMGSolver::solve(Foam::Field<double>&, Foam::Field<double> const&, unsigned char) const at ??:? #6 Foam::fvMatrix<double>::solveSegregated(Foam::dictionary const&) at ??:? #7 Foam::fvMatrix<double>::solveSegregatedOrCoupled(Foam::dictionary const&) at ??:? #8 Foam::fvMesh::solve(Foam::fvMatrix<double>&, Foam::dictionary const&) const at ??:? #9 Foam::fvMatrix<double>::solve() at ??:? #10 ? at ??:? #11 __libc_start_main in /lib64/libc.so.6 #12 ? at ??:? Furthermore I'm thinking about the outlet boundary conditions. I guess there is backflow in some parts of the outlet. So I set the type to inletOutlet in 0/U. But I have no idea which inletValue I can use. For k and omega the zeroGradient at the outlet might also be problematic. 

November 24, 2021, 16:15 

#6 
Senior Member

Do you require a waveTransmissive boundary condition for the pressure at the outlet? See https://openfoamwiki.net/index.php/H...dary_condition


November 25, 2021, 08:41 

#7 
Member
Daniel
Join Date: Jan 2021
Posts: 39
Rep Power: 5 
Hey,
you tried a lot, thats true. RhoSimpleFoam is kind of special and very sensitive. Give a transient calculation with rhoPimple a try, it's much more robust and versatile. Your log file indicates, that your timeStepErrors are really high ( around 10^7 bigger then they should), also you have high bounding values in k and omega. What velocities (maximium) are you expecting in your domain? Simplefoam should give you a value there. Is it really near the transonic region of your fluid (fvSolution transonic  yes should always be off most times). What are your timeStepErrors and Residuals in SimpleFoam? Btw: this solver is so robust, it runs with most settings. 

November 25, 2021, 11:08 

#8 
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I'm really glad to get your feedback  thank you. This helps a lot.
In the meanwhile I was able to check two things: 1. I was unsure about the right usage of the waveTransmissive boundary condition. So I added a really long duct at the outlet to move the place for the zeroGradient boundary condition far away from the nozzle throat  expecting the flow to be more homogeneous there. And indeed this results in a very smooth convergence for lower mass flow rates (about 1/10 of the actual flow rate). 2. When I then ramp the mass flow rate to higher values this seems to be okay up to 1/4 of the actual flow rate. Then the residuals rise again, turbulence and temperature become bounded and at last I get a floating point exception. Here are the last steps from the log: Code:
Time = 10007 smoothSolver: Solving for Ux, Initial residual = 0.682938315105, Final residual = 0.000287364778599, No Iterations 1000 smoothSolver: Solving for Uy, Initial residual = 0.682938327772, Final residual = 0.000335502672822, No Iterations 1000 smoothSolver: Solving for Uz, Initial residual = 0.956672521947, Final residual = 0.0287743274877, No Iterations 1000 smoothSolver: Solving for e, Initial residual = 1, Final residual = 0.00171898979327, No Iterations 1000 limitTemperature temperature_constraints Lower limited 4332 (2.01254355401%) of cells limitTemperature temperature_constraints Upper limited 10694 (4.96817653891%) of cells limitTemperature temperature_constraints Unlimited Tmax 5000 Unlimited Tmin 1 GAMG: Solving for p, Initial residual = 0.248165319778, Final residual = 1.69988878639e05, No Iterations 18 time step continuity errors : sum local = 9.08666371988e+32, global = 7.09410752815e+18, cumulative = 7.09410752815e+18 smoothSolver: Solving for omega, Initial residual = 0.555683310243, Final residual = 7.65079881608e06, No Iterations 1000 bounding omega, min: 2.22543731148e+24 max: 3.73801862533e+24 average: 6.25428322118e+19 smoothSolver: Solving for k, Initial residual = 0.190530340693, Final residual = 8.86466389855e09, No Iterations 99 bounding k, min: 45650036586.1 max: 1.09206304413e+12 average: 19063766.1197 ExecutionTime = 20.13 s ClockTime = 20 s Time = 10008 smoothSolver: Solving for Ux, Initial residual = 0.337580144242, Final residual = 0.000100646177355, No Iterations 1000 smoothSolver: Solving for Uy, Initial residual = 0.337548080513, Final residual = 9.32237768003e05, No Iterations 1000 smoothSolver: Solving for Uz, Initial residual = 0.307343200808, Final residual = 0.00266242950238, No Iterations 1000 smoothSolver: Solving for e, Initial residual = 1, Final residual = 5.65715128871e08, No Iterations 1000 limitTemperature temperature_constraints Lower limited 115602 (53.7059233449%) of cells limitTemperature temperature_constraints Upper limited 3259 (1.51405342625%) of cells limitTemperature temperature_constraints Unlimited Tmax 5000 Unlimited Tmin 1 GAMG: Solving for p, Initial residual = 0.952214969982, Final residual = 6.07324943602e05, No Iterations 9 time step continuity errors : sum local = 1.24414784332e+47, global = 2.24296712762e+33, cumulative = 2.24296712762e+33 smoothSolver: Solving for omega, Initial residual = 0.000916815161875, Final residual = 7.5135316827e09, No Iterations 33 bounding omega, min: 7.36369332318e+32 max: 7.45087842067e+34 average: 8.45192123834e+29 smoothSolver: Solving for k, Initial residual = 0.0652221006548, Final residual = 9.86389746847e09, No Iterations 27 bounding k, min: 7.95004417902e+19 max: 2.54187707242e+21 average: 2.49264192669e+16 ExecutionTime = 27.47 s ClockTime = 28 s Time = 10009 smoothSolver: Solving for Ux, Initial residual = 0.707100864244, Final residual = 8.17380806564e09, No Iterations 34 smoothSolver: Solving for Uy, Initial residual = 0.707102511597, Final residual = 8.09615585829e09, No Iterations 34 smoothSolver: Solving for Uz, Initial residual = 0.677345826642, Final residual = 3.47383376751e07, No Iterations 1000 smoothSolver: Solving for e, Initial residual = 1, Final residual = 4.84816984568e09, No Iterations 18 limitTemperature temperature_constraints Lower limited 99354 (46.1574912892%) of cells limitTemperature temperature_constraints Upper limited 10946 (5.08524970964%) of cells limitTemperature temperature_constraints Unlimited Tmax 5000 Unlimited Tmin 1 GAMG: Solving for p, Initial residual = 0.652473647695, Final residual = 5.7463368848e05, No Iterations 16 time step continuity errors : sum local = 1.15109831238e+56, global = 9.67393479366e+41, cumulative = 9.67393477123e+41 smoothSolver: Solving for omega, Initial residual = 0.71639185423, Final residual = 5.03738174817e09, No Iterations 14 bounding omega, min: 9.40492911923e+29 max: 9.37100865931e+33 average: 4.10924824413e+29 smoothSolver: Solving for k, Initial residual = 0.742849536333, Final residual = 6.31077894166e09, No Iterations 13 bounding k, min: 9.91457445321e+18 max: 2.28501407243e+21 average: 3.36552987043e+16 ExecutionTime = 29.96 s ClockTime = 30 s Time = 10010 smoothSolver: Solving for Ux, Initial residual = 0.629389455891, Final residual = 3.12801623638e06, No Iterations 1000 smoothSolver: Solving for Uy, Initial residual = 0.629388913105, Final residual = 1.98095241143e06, No Iterations 1000 smoothSolver: Solving for Uz, Initial residual = 0.925952525366, Final residual = 2.71850304045e08, No Iterations 1000 smoothSolver: Solving for e, Initial residual = 1, Final residual = 8.7328752983e09, No Iterations 31 limitTemperature temperature_constraints Lower limited 5227 (2.42833914053%) of cells limitTemperature temperature_constraints Upper limited 149022 (69.2320557491%) of cells limitTemperature temperature_constraints Unlimited Tmax 5000 Unlimited Tmin 1 GAMG: Solving for p, Initial residual = 0.539866259316, Final residual = 4.9318115972e05, No Iterations 9 time step continuity errors : sum local = 6.43187006542e+68, global = 1.16146455737e+54, cumulative = 1.16146455737e+54 smoothSolver: Solving for omega, Initial residual = 0.000345869080579, Final residual = 9.58730961687e09, No Iterations 6 bounding omega, min: 1.51533821371e+32 max: 1.49080821324e+34 average: 8.06873195342e+29 smoothSolver: Solving for k, Initial residual = 0.000147693344574, Final residual = 7.64781028605e09, No Iterations 5 bounding k, min: 3.03356951287e+19 max: 1.75336888299e+21 average: 6.53704323548e+16 ExecutionTime = 35.49 s ClockTime = 36 s Time = 10011 smoothSolver: Solving for Ux, Initial residual = 0.66610414697, Final residual = 0.000621669998517, No Iterations 1000 smoothSolver: Solving for Uy, Initial residual = 0.666103047247, Final residual = 0.000410915153699, No Iterations 1000 smoothSolver: Solving for Uz, Initial residual = 0.632811666534, Final residual = 72.2468595028, No Iterations 1000 smoothSolver: Solving for e, Initial residual = 1, Final residual = 6.21515996553e09, No Iterations 18 limitTemperature temperature_constraints Lower limited 57763 (26.8353077816%) of cells limitTemperature temperature_constraints Upper limited 66936 (31.0968641115%) of cells limitTemperature temperature_constraints Unlimited Tmax 5000 Unlimited Tmin 1 GAMG: Solving for p, Initial residual = 0.39167792921, Final residual = 2.5286286111e05, No Iterations 12 time step continuity errors : sum local = 5.46160355531e+83, global = 1.16422002872e+68, cumulative = 1.16422002872e+68 smoothSolver: Solving for omega, Initial residual = 3.70809948994e05, Final residual = 4.5090165572e09, No Iterations 10 bounding omega, min: 3.26955250853e+39 max: 1.38304174851e+41 average: 1.06914348437e+36 smoothSolver: Solving for k, Initial residual = 1.48407726826e05, Final residual = 3.2271897245e09, No Iterations 11 bounding k, min: 7.45554271837e+23 max: 8.11191480185e+28 average: 5.8911348066e+23 ExecutionTime = 41.1 s ClockTime = 41 s Time = 10012 smoothSolver: Solving for Ux, Initial residual = 0.793459788924, Final residual = 7.71857459656e09, No Iterations 37 smoothSolver: Solving for Uy, Initial residual = 0.793459473542, Final residual = 7.71856327155e09, No Iterations 37 smoothSolver: Solving for Uz, Initial residual = 0.560225739981, Final residual = 7.75970306657e09, No Iterations 39 smoothSolver: Solving for e, Initial residual = 1, Final residual = 2.5198167101e07, No Iterations 1000 limitTemperature temperature_constraints Lower limited 118319 (54.9681765389%) of cells limitTemperature temperature_constraints Upper limited 42348 (19.6738675958%) of cells limitTemperature temperature_constraints Unlimited Tmax 5000 Unlimited Tmin 1 GAMG: Solving for p, Initial residual = 0.712697558163, Final residual = 7.10567897157e05, No Iterations 19 time step continuity errors : sum local = 1.18719938884e+91, global = 6.57209032417e+76, cumulative = 6.57209031253e+76 smoothSolver: Solving for omega, Initial residual = 0.0454299588808, Final residual = 6.46035024839e09, No Iterations 23 bounding omega, min: 1.84987790127e+39 max: 1.00064926973e+43 average: 9.17667453186e+37 smoothSolver: Solving for k, Initial residual = 0.0385242789961, Final residual = 8.17381323816e09, No Iterations 9 bounding k, min: 1.23972360477e+32 max: 1.08563089711e+33 average: 8.83847936331e+27 ExecutionTime = 43.64 s ClockTime = 44 s Time = 10013 smoothSolver: Solving for Ux, Initial residual = 0.497624650435, Final residual = 4.87058969705e09, No Iterations 29 smoothSolver: Solving for Uy, Initial residual = 0.497903225512, Final residual = 4.86876696485e09, No Iterations 29 smoothSolver: Solving for Uz, Initial residual = 0.570478907314, Final residual = 9.52400499797e09, No Iterations 30 smoothSolver: Solving for e, Initial residual = 1, Final residual = 8.24709699828e09, No Iterations 26 limitTemperature temperature_constraints Lower limited 119153 (55.3556329849%) of cells limitTemperature temperature_constraints Upper limited 65867 (30.600232288%) of cells limitTemperature temperature_constraints Unlimited Tmax 5000 Unlimited Tmin 1 GAMG: Solving for p, Initial residual = 0.743150135483, Final residual = 4.20822840176e05, No Iterations 5 time step continuity errors : sum local = 9.2987226444e+95, global = 6.03048038874e+81, cumulative = 6.03041466784e+81 smoothSolver: Solving for omega, Initial residual = 1.4758490331e06, Final residual = 6.68083715593e09, No Iterations 7 bounding omega, min: 3.6782010718e+42 max: 9.50602386695e+43 average: 1.17393202904e+39 smoothSolver: Solving for k, Initial residual = 1.04960751006e08, Final residual = 4.77378562102e09, No Iterations 4 bounding k, min: 2.68770735334e+32 max: 4.51128912912e+33 average: 6.12559229196e+28 ExecutionTime = 44.5 s ClockTime = 45 s Time = 10014 smoothSolver: Solving for Ux, Initial residual = 0.544102085423, Final residual = 8.9839774487e09, No Iterations 23 smoothSolver: Solving for Uy, Initial residual = 0.544070041353, Final residual = 8.98402588636e09, No Iterations 23 smoothSolver: Solving for Uz, Initial residual = 0.549530349327, Final residual = 5.34064788471e09, No Iterations 23 smoothSolver: Solving for e, Initial residual = 1, Final residual = 0.00211127002229, No Iterations 1000 limitTemperature temperature_constraints Lower limited 96275 (44.7270615563%) of cells limitTemperature temperature_constraints Upper limited 118290 (54.9547038328%) of cells limitTemperature temperature_constraints Unlimited Tmax 5000 Unlimited Tmin 1 GAMG: Solving for p, Initial residual = 0.244574783005, Final residual = 1.80656793475e05, No Iterations 19 time step continuity errors : sum local = 1.50876019421e+102, global = 1.32173121908e+87, cumulative = 1.32172518866e+87 smoothSolver: Solving for omega, Initial residual = 1.43058998943e05, Final residual = 6.0894017599e09, No Iterations 4 bounding omega, min: 7.92551170334e+42 max: 3.92247524649e+43 average: 6.2522736871e+38 smoothSolver: Solving for k, Initial residual = 3.55770947532e07, Final residual = 4.62807131238e09, No Iterations 2 bounding k, min: 9.74285631755e+32 max: 4.12723898701e+34 average: 2.58919841857e+29 ExecutionTime = 46.95 s ClockTime = 47 s Time = 10015 smoothSolver: Solving for Ux, Initial residual = 0.51964422401, Final residual = 0.00660365318865, No Iterations 1000 smoothSolver: Solving for Uy, Initial residual = 0.519658858041, Final residual = 0.00783449220059, No Iterations 1000 smoothSolver: Solving for Uz, Initial residual = 0.319326144599, Final residual = 0.00035545345465, No Iterations 1000 [2] #0 Foam::error::printStack(Foam::Ostream&) at ??:? [2] #1 Foam::sigFpe::sigHandler(int) at ??:? [2] #2 ? in /lib64/libpthread.so.0 [2] #3 Foam::multiply(Foam::Field<double>&, Foam::UList<double> const&, Foam::UList<double> const&) at ??:? [2] #4 Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > Foam::operator*<Foam::fvPatchField, Foam::volMesh>(Foam::tmp<Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> > const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) at ??:? [2] #5 Foam::fv::boundedConvectionScheme<double>::fvcDiv(Foam::GeometricField<double, Foam::fvsPatchField, Foam::surfaceMesh> const&, Foam::GeometricField<double, Foam::fvPatchField, Foam::volMesh> const&) const at ??:? [2] #6 ? at ??:? [2] #7 ? at ??:? [2] #8 __libc_start_main in /lib64/libc.so.6 [2] #9 ? at ??:? I tried the simpleFoam incompressible solver. This one gives nice convergence and time step continuity errors around 1e4 as you can see in this log: Code:
Time = 1497 smoothSolver: Solving for Ux, Initial residual = 0.000100500888787, Final residual = 8.90568075304e06, No Iterations 6 smoothSolver: Solving for Uy, Initial residual = 0.00100435845354, Final residual = 8.95753961279e05, No Iterations 6 smoothSolver: Solving for Uz, Initial residual = 0.000578782900718, Final residual = 5.17059123177e05, No Iterations 6 GAMG: Solving for p, Initial residual = 0.000307317720265, Final residual = 2.73690798359e05, No Iterations 3 time step continuity errors : sum local = 0.0314680286054, global = 0.000215929883069, cumulative = 17.0819715067 smoothSolver: Solving for omega, Initial residual = 0.000189409035749, Final residual = 1.53940593495e05, No Iterations 2 smoothSolver: Solving for k, Initial residual = 0.000239689487637, Final residual = 2.09473499003e05, No Iterations 6 ExecutionTime = 888.39 s ClockTime = 889 s Time = 1498 smoothSolver: Solving for Ux, Initial residual = 0.000100341349694, Final residual = 8.89145140224e06, No Iterations 6 smoothSolver: Solving for Uy, Initial residual = 0.00100288646037, Final residual = 8.94435032349e05, No Iterations 6 smoothSolver: Solving for Uz, Initial residual = 0.000577551294907, Final residual = 5.16052069827e05, No Iterations 6 GAMG: Solving for p, Initial residual = 0.000307355450312, Final residual = 2.80029736407e05, No Iterations 3 time step continuity errors : sum local = 0.0321770726825, global = 0.000101536466035, cumulative = 17.0818699703 smoothSolver: Solving for omega, Initial residual = 0.000186158849077, Final residual = 1.57109669246e05, No Iterations 2 smoothSolver: Solving for k, Initial residual = 0.000239410721694, Final residual = 2.09196646412e05, No Iterations 6 ExecutionTime = 888.97 s ClockTime = 890 s Time = 1499 smoothSolver: Solving for Ux, Initial residual = 0.000100190439595, Final residual = 8.8780677202e06, No Iterations 6 smoothSolver: Solving for Uy, Initial residual = 0.00100123785007, Final residual = 8.92963811531e05, No Iterations 6 smoothSolver: Solving for Uz, Initial residual = 0.000576308406416, Final residual = 5.14990578231e05, No Iterations 6 GAMG: Solving for p, Initial residual = 0.000306761427373, Final residual = 2.71315079717e05, No Iterations 3 time step continuity errors : sum local = 0.0311601766532, global = 0.000192217775192, cumulative = 17.082062188 smoothSolver: Solving for omega, Initial residual = 0.000192195856679, Final residual = 1.54182053449e05, No Iterations 2 smoothSolver: Solving for k, Initial residual = 0.000239151556127, Final residual = 2.08927250343e05, No Iterations 6 ExecutionTime = 889.55 s ClockTime = 890 s Time = 1500 smoothSolver: Solving for Ux, Initial residual = 0.000100031217945, Final residual = 8.86382202319e06, No Iterations 6 smoothSolver: Solving for Uy, Initial residual = 0.000999777848919, Final residual = 8.9165314016e05, No Iterations 6 smoothSolver: Solving for Uz, Initial residual = 0.000575137221727, Final residual = 5.13952295765e05, No Iterations 6 GAMG: Solving for p, Initial residual = 0.000307531956787, Final residual = 2.76136481807e05, No Iterations 3 time step continuity errors : sum local = 0.0316947674859, global = 5.90868822675e05, cumulative = 17.0820031012 smoothSolver: Solving for omega, Initial residual = 0.00019415877079, Final residual = 1.5487326225e05, No Iterations 2 smoothSolver: Solving for k, Initial residual = 0.00023881617953, Final residual = 2.08642842142e05, No Iterations 6 ExecutionTime = 890.13 s ClockTime = 891 s SIMPLE solution converged in 1500 iterations From the simpleFoam solution I would expect max. velocities around 600 m/s. Fluent calculates a max. velocity of 542 m/s for the compressible case with the same flow rate. So the transonic option might be justified. I will try the rhoPimpleFoam next and the waveTransmissive bc if I find some useful values for the parameters. 

November 25, 2021, 13:51 

#9 
Senior Member

We have found below to work well.
Here fieldInf 101325 is the initial value for the pressure on the domain. Good luck! Outlet { type waveTransmissive; psi thermosi; lInf 1; field p; gamma 1.4; fieldInf 101325; value $internalField; } 

November 26, 2021, 05:47 

#10 
Member
Daniel
Join Date: Jan 2021
Posts: 39
Rep Power: 5 
Okay, so SimpleFoam works good and accurate as necessary. The timeStepErrors are related to the pressure tolerance, so squeezing this will result in lower values.
For your problem with rhoSimple: Your log FIle indicates, that your residuals are really high after 10000 Iterations, the turbulence values are extraordinary, so BC´s maybe the real issue here. Take into consideration, that your BC´s are not perfect for these very high velocities, but i am not sure, which to choose. Give these fromDomenico a try. My guess is, that at these velocities, the steady solver just comes to a problem. This case is so dependend on time, that neglectimg these terms actually causes divergence. 

March 30, 2022, 01:21 

#11 
New Member
anonymous
Join Date: Mar 2022
Posts: 2
Rep Power: 0 
HI,
Could you please post your BCs and system folder of simpleFoam case? i am too trying to simulate a pressure driven flow and i am kinda stuck because of bounding of k/epsilon TIA 

Tags 
boundaries, compressible air, rhosimplefoam, turbuelence model 
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